MicroRNAs are typically small RNA molecules of generally about nineteen to twenty-five nucleotides in length. These microRNAs are non-coding RNAs which are cleaved from hairpin precursors. Several microRNAs have been identified in the genomes of a wide range of multicellular life forms.
MicroRNAs in animals are found in diverse genomic locations. Typically, most microRNAs are encoded in intergenic regions. Other microRNAs are hosted within the introns of mRNAs or within non-coding RNA transcripts.
Many microRNAs are conserved in sequence between distantly related organisms, and exhibit tissue-specific or developmental stage-specific expression. The conservation of the sequence between organisms indicates that microRNAs may play important roles in biological processes.
MicroRNA molecules have been reported to control gene expression in a sequence specific manner in a wide variety of organisms by blocking translation after partially hybridizing to the non-coding 3′ region of mRNAs of target genes. The genes targeted by microRNAs largely remain to be characterized.
However, there is growing evidence that microRNAs are implicated in various diseases and illnesses. For instance, Drosophila microRNAs have been shown to target genes involved in apoptosis. Also, B-cell chronic lymphocytic leukemia has been linked to the deletion of two microRNAs.
Therefore, it is important to elucidate the mechanisms involved in mediating genes which play a role in the regulation of various diseases and illnesses. Thus, there is a need for materials and methods that can help elucidate the function of regulators, such as microRNAs, in various diseases and illnesses.
Further, due to the ability of microRNAs to induce RNA degradation or repress translation of mRNA which encode important proteins, there is also a need for novel molecules that inhibit microRNA-induced cleavage or promote expression by inhibiting translational repression of target mRNAs.